Question

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Instruction cycle is defined as the time required to complete the execution of an instruction. Reason (R): The 8085 instruction cycle consists of three to six machine cycles. In the light of the above statements, choose the most appropriate answer from the options given below :

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• C. (A) is correct but (R) is not correct
• D. (A) is not correct but (R) is correct

Hint:

Instruction cycle: \[ \text{Fetch + Decode + Execute} \] Machine cycle: \[ \text{Smaller operation inside instruction execution} \]

Answer 1

The Correct Option is B

Concept: An instruction in a microprocessor is executed through a sequence of operations known as:
• Fetch
• Decode
• Execute The total time required for these operations is called the instruction cycle.

Step 1: Examine Assertion (A). Assertion states: \[ \text{Instruction cycle = time required to complete execution of an instruction} \] This statement is absolutely correct. An instruction cycle includes:
• Fetching instruction from memory
• Decoding instruction
• Executing instruction
• Storing result if necessary Therefore: \[ \boxed{\text{Assertion (A) is correct}} \]

Step 2: Examine Reason (R). The reason states: \[ \text{8085 instruction cycle consists of three to six machine cycles} \] This statement is also generally correct because:
• Different instructions require different numbers of machine cycles.
• Complex instructions take more cycles. Thus: \[ \boxed{\text{Reason (R) is correct}} \]

Step 3: Check whether Reason explains Assertion. The reason merely states: \[ \text{Number of machine cycles in 8085} \] But it does not explain: \[ \text{Definition of instruction cycle} \] Hence:
• Both statements are true.
• But Reason is not the correct explanation of Assertion.

Step 4: Write final conclusion. Therefore the correct option is: \[ \boxed{(B)} \]